Hydrogen thyratron improvement



Sept. 3, 1957 K. NIENHUIS ,8

HYDROGEN THYRATRON IMPROVEMENT .Filed DEC- 22. 1952 INVENTOR. Kozwizzzs 1 1M075.

HYonoonN THYRATRON IMPRGVEMENT Korneiis Nienhuis, Eindhoven, Netherlands, assignor, by

mesne assignments, to North American Philips Co r-- pany, Inc, New York, N. Y., a corporation of Delaware Application December 22, 1952, Serial No. 327,220 Claims. (Cl. 313--3) The present invention relates generally to electric discharge devices and more particularly to improvements in the electrode structure and associated shields and baflles for electric discharge devices making use of an ionizable medium.

When operating an electric discharge device with intermittent voltages, a number of requirements .are imposed on the device which are not encountered in continuous operation. Thus where a hydrogen thyratron is incorporated in a pulse modulator adapted to produce voltage pulses of extremely short duration for energizing a magnetron, it is essential that the thyratron be capable of firing instantaneously in response to applied ignition impulses. It is important, moreover, that the thyratron be responsive not only to ignition voltages of high magnitude but also to grid triggering impulses of relatively low magnitude and under varying conditions of anode potential.

Accordingly, it is the principal object of the invention to provide an improved electric discharge device employing an ionizable medium and having a stable and rapid firing characteristic to satisfy the above-described requirements.

More specifically, it is an object of the invention to provide a hydrogen thyratron possessing an improved electrode structure and associated shields and baflles.

Still another object of the invention is to atford an electrode structure for a thyratron in which the electron stream emanating from the cathode surface is subjected to electronoptical concentration, whereby a rapid triggering action is effectuated.

Briefly stated, these objects are attained in a preferred embodiment of an electrode structure for a thyratron wherein a grid bafile is interposed between the control grid element and the open end of the cathode assembly, said baille having a circular opening formed therein. The cathode assembly includes an electron emissive element surrounded by a shield open at one end. The upper end of the shield is provided with a conically shaped section, circular plates being disposed Within the conical section of the shield to partially close the annular space between the cathode element and the Wall of the shield, thereby to define an electron focusing passage. This focusing passage serves to concentrate the electron stream toward the opening in the baffle where the electrons enter the ironization region of the device.

For a better understandin of the invention as well as other objects and further features thereof, reference is made to the following detailed description to be read in conjunction with the accompanying drawing, wherein:

Fig. 1 is a sectional view of a thyratron in accordance with the invention;

Fig. 2 is a plan view of the grid bafile in the device; and

Fig. 3 is a plan view of the upper end of the cathode assembly of the device.

Referring now to the drawing, there is shown an electric discharge device comprising a generally cylindrical ice vitreous envelope 10 having an insulating base 11 secured to one end thereof. Base 11 is provided with the usual contact prongs 12, only two of which are shown herein. The electrode structure of the device is supported between a stem press 13 disposed in the lower end of the envelope and a hollow glass rod 14 depending from the upper end of envelope 10.

An anode 15 which is preferably disc-shaped is supported by a lead-in conductor 16, which passes centrally through glass rod 14 and is firmly secured therein by a reentrant portion 14'. The lead-in conductor 16 terminates in a metal cap 17 which is cemented or otherwise sealed to the upper end of the envelope. The mode may, as is conventional, be fabricated of nickel or similar material.

The cathode assembly, generally designated by reference numeral 18, is supported from press 13 by rigid conductors l9 and 20. Conductor 20 is extended to provide a connection via a flexible lead to one of the prongs 12 for external cathode connection. The discharge space between anodelS and the cathode assembly 18 is totally enclosed by a grid structure of generally cylindrical form. As illustrated in the drawing, the structure comprises a cylindrical enclosure having a lower cylindrical section 21 in the form of a sheet metal band and an upper cylina drical section 22 aflixed thereto and formed by a metallic mesh or a foraminated band. The upperend of the grid structure is closed by a header 23 having a central eyelet extension 24 which is secured to the lower end of rod 14 by means of a suitable clamp 25 which may be tightened by a screw 25 joining the ends of the clamp. The lower end or" the grid cylinder is supported from stem press 13 by means of rigid conductors 26 and 27, con- J ductor 26 being extended and connected by a flexible lead to another one of prongs 12 for external grid connection.

The control grid of the device is constituted by an annular disc 23 which is transversely disposed within the grid enclosure and positioned adjacent anode 15. The

disc 28 is provided with a peripheral flange 28' which is Welded to the inner wall of the upper section 22 of the grid enclosure. Covering the central opening in disc 28;

and attached to the under face thereof is a wire grid 29 through which the discharge takes place.

Positioned intermediate control grid 28 and the open upper end of the cathode assembly 18 is .a transverse'grid bafile 30, the baflle being shown separately in Fig. 2.

This bathe is welded to the peripheral flange 28' of the control grid and is provided with three arcuate openings. 31 arranged in a circular configuration.

The envelope is first evacuated in accordance withthe' usual practice by means of a narrow tube 32 communieating with the envelope through press 13 and is then charged with an ionizable medium. This ionizable medium is preferably a gas such as hydrogen under a pressure of two hundred to several hundred microns.

accordance with the invention makes possible an increased gas pressure as compared to prior art devices.

The cathode assembly 18 is constituted by an enclosed.

cathode cylinder 33 whose exterior surface is coatedwith material acting as a good source of electrons when heated to a predetermined temperature. Such heating is effected by a helical heating element 34 centrally mounted In. this" regard, it is pointed out that the electrode structure in.

3 oxides. I Cathode cylinder 33 is supported coaxially within a cylindrical heat shield structure which is open at one end and is constituted by a cylindrical inner member 35 and a cylindrical outer member 36 concentrically spacedtherefrom and having a height exceeding tb'at'of the inner-member. V r

In order to eife'ct an electron-optical concentration the electrons emanating from the surface of cathode cylinder 33 whereby the electrons are directed through the circular passage in grid bafile 30 into the ionization region existing between anode and the grid cafr'le, the upper end portion of outer shield member 36 is flared outwardly to form' a conical shield 36'.

As shown separately in Fig. 3, positioned concentrically Within conical shield 36' are two circular heat shielding plates 38 and 39 of like diameter, plate 38 being supported by a strut 37 whose extremities are welded to the inner wall of outer shield member 36. Plate 38 is maintained in spaced relation with respect to plate 39 and is welded thereto, this being accomplished by providing plate 38 with a central indentation. The diameter of plates 38 and 39 is'substantially larger than that of the cathode cylinder 33, thereby partially closing the annular space between the cathode cylinder and conical shield 36'. 7

Thus the electron stream emanating from the cathode is concentrated within the annular and conical passage formed betweenthe inner wall of conical shield 36' and plates 38 and 39, the concentrated stream being projected through the circular opening 31 in grid bafile to enter the ionization region.

While there has been disclosed what at present is a preferred embodiment of the invention, it is obvious that many changes may be made therein without departing from the essential conception.

What is claimed is:

1. An electric discharge device comprising an anode; a cathode assembly including a cathode element having an emissive surface, a cylindrical shield surrounding said element and open at one end, said shield at said open end having a conical shape for concentrating the electron stream form said cathode element, and a plate partially closing the annular space between said element and the wall of said shield, said plate being supported adjacent the end of the element at the open end of said shield; and a grid structure enclosing said anode and said cathode assembly and provided with a control grid member adjacent said anode and a bafile interposed between said control grid and said cathode assembly, said baffle having a circular opening concentric with said conical shield.

. 2. An electric discharge device comprising an anode; a cathode assembly including a cathode element having an emissive surface, a cylindrical shield surrounding said element and open at one end, said shield at said open end having a conical shape for concentrating the electron stream from said cathode element, and a circular plate partially closing the annular space between said element and the wall of said shield, said plate being supported adjacent the end of the element at the open end of said shield; and a cylindrical grid structure enclosing said anode and said cathode assembly and provided with a disc-shaped control grid member transversely mounted on said structure adjacent said anode, and a bafile having a circular opening transversely mounted adjacent said conical section of said shield.

3. A hydrogen thyran'on comprising an anode; a cathode assembly including a cathode element provided with an enclosed cylinder having an electron emissive coating,

a cylindrical heat shield structure coaxially surrounding said element and open at one end and including an inner shield and an outer shield spaced therefrom, said outer shield at the open end thereof having a conical shape to efiect electron concentration, and a circular plate partially closing the annular space between said element and the wall and being supported adjacent the end of the element at the open end of the shield structure; and a grid structure surrounding both said anode and said cathode assembly and including a cylindrical enclosure coaxially positioned with respect to said shield structure and said anode, a portion of said enclosure adjacent said anode being of foramincus construction, a disc-shaped control grid transversely mounted in said enclosure adjacent said anode and a disc-shaped baflle transversely mounted in said enclosure between said control grid and the open end of said cathode assembly, said baffle having a circular opening therein.

4. A hydrogen thyratron comprising a hydrogen-filled envelope; an anode; a cathode assembly including a cathode element provided with an enclosed cylinder having an electron emissive coating, a cylindrical heat shield structure coaxially surrounding said element and open at one end and including an inner shield and an outer shield spaced therefrom, said outer shield at the open end thereof having a conical shape to effect electron concentration, and two spaced circular plates partially closing the annular space between said element and the wall and supported adjacent the end of the element at the open end of the shield structure; and a grid structure surrounding both said anode and said cathode assembly and including a cylindrical enclosure coaxially positioned with respect to said shield structure and said anode, a portion of said wall adjacent said anode being of foraminous construction, a disc-shaped control grid transversely mounted in said enclosure adjacent said anode and a disc-shaped baflie transversely mounted in said enclosure between said control grid and the open end of said cathode assembly, said bafi'le having a circular opening therein concentric with the conical section of said shield.

5. A gas-filled discharge device comprising a cathode having an electron emissive surface, a control grid and an anode mounted in that order, a shield member surrounding the cathode, a centrally disposed solid plate disposed adjacent the end of said cathode and defining with said shield member a substantially annular passageway for electrons from saidcathode, said shield member having an outwardly flaring end adjacent said passageway, and a bafiie member disposed between the solid plate and the control grid, said baflie member having annular openings therein only adjacent the periphery thereof and approximately aligned with the annular passageway for the passage of electrons in a concentrated stream to the space containing the control grid.

References Cited in the file of this patent UNITED STATES PATENTS 1,869,829 Skellett et a1. Aug. 2, 1932 2,121,591 Gessford et a1. June 21, 1938 2,303,166 Laico Nov. 24, 1942 2,399,003 Crapuchettes Apr. 23, 1946 2,436,265 Pohle et al. Feb. 17, 1948 2,479,529 Watrous et al. Aug. 16, 1949 2,497,911 Reilly et a1. Feb. 21, 1950 2,518,879 Germeshausen Aug. 15, 1950 2,650,998 Watrous Sept. 1, 1953 2,653,261 Watrous Sept. 22, 1953 

